Milling machine



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MILLING MACHINE Filed Sept. 12, 1934 11 sheets-sheet 11 kum Moron T2 T sLEFT 'Patented Jail. 26,1953? A UNITED STATES PATENT OFFICE i 2,068,840MILLING MACHINE Arthur F. Bennett, West Barrington, and August L.Krause, Providence, R. I., assignors to Brown and Sharpe ManufacturingCompany, a corporation of Rhode Island Application september 12, 1934,serial No. 743,652

3'6 Claims.

electrically driven and is mounted on'a carriage for verticaladjustmentl toward and away from the table.

It is a. principal object of the present invention to provide novel andimproved means for controlling the operation of the work supportingtable and cutter spindle to permit a more eilicient and safemanipulation of the machine by the operator, and also to vinsure a highdegree of efflciency and accuracy in operation.

It is a further object of the invention to provide certain novel and'improved features of construction and operation of the severalcooperating mechanisms of the machine to produce a better and moreeilicient machine.

With these and other objects inview,vas may hereinafter appear, certainfeatures of the invention are concerned with the provision of a noveland improved electrical control mechanism for the machine, and morespecifically with the provision of an improved switch mechanism forcontrolling the starting and stopping'of the table and spindle motors. lv

In order to secure a more accurate control in the stopping of therelatively high speed motors utilized, one feature of the inventionconsists in the provision of a novel and improved viscosity .switchwhich may be mounted directly -on the armature shaft of the motor, andis well adapted for consistent and efficient operation at the high speedof rotation developed by the motor shaft.

Another feature of the invention consists in the' provision ofelectrical control mechanism for controlling the operation of aviscosity plugging l switch to prevent over-travel of the switchmechanism in plugging the motor to a stop, with a consequent tendencyfor the motor to kick in a in the provision of a novel safety stopswitch for the table motor and a jog switch for the spindle by theoperator.

motor which serve to permit a more versatile land complete control ofthe operation of the machine Another feature of the present inventionconsists in the provision of a novel and improved pick-olf gear casewhich is well adapted to facilitate the changing of gears, and is-soarranged as to prevent movement of the table drivingconnectionsincluding the gears under power with possible injury to themperatorwhile the ,gear case is open.

Thev several features of the present invention consist also in thedevices, combinations and arrangement of parts hereinafter -describedand claimed, which together with the advantages to be obtained therebywill be readily understood by one skilled in the art from the followingdescrip tion taken in connection with the accompanying drawings', inwhich Fig. 1 is a view in front elevation of a manufacturing typemilling machine; Fig. 2 is a detail end view of the auxiliary base orcoolant trough; Fig. 3 is a plan view of the coolant trough shown inFig. 2; Fig. 4 isa. detail View in fronti elevation illustratingparticularly the control box yand switches contained therein forcontrolling the operation of the table, with mechanism Afor stopping thetable upon opening of the pick-off gear casing; Fig. 5 is a detailsectional view taken on the line 5-5 of Fig. 4; Fig.

6 is a detail sectional view on the line 6-6 of 30 Fig. 4; Fig. 7 is adetail sectional view taken on .the line 'l--l of Fig'. 4; Fig. 8 is adetail sectional plan view taken on the line 8--8 of Fig. 7; Fig.

9 is an enlarged` detail view of the face of the control box; Fig. 10 isa detail sectional view in 35' front elevation illustrating particularlythe driving connections for operating the table; Fig. 1i

' is a sectional plan view taken on the line lI-II Fig. 16 is a view inrear elevation partly in sec- 45y tion of the cutter spindle unitincluding the spindle motor and driving connections; Fig. 1'? lis an,enlarged detail sectional view of the viscosity switch shown in Fig. 16;Fig. 18 is aneularged detail sectional plan view ofthe spindle motorbrake taken on the line I8|8 of Fig. 16; Fig. 19 is a sectional viewAtaken on the line I9-|9 of Fig. 16; Fig. 20 is a detail sectional viewof the spindle motor brake solenoid taken on the line Inf-26 of Fig.`19;',Flg. 21 is an enlargedview in side elevation of the spindle motorviscosity switch taken on the line 2l-2I of Fig. 16; Fig. 22 is asectional plan view taken on the line 22--22 ,of Fig. 21; Fig. 23 is adiagrammatic view of the electrical connections for controlling theoperation of the table and cutter spindle; and Fig. 24 is. anAexplanatory diagram of the electrical connections illustrated in Fig.23.

The milling machine herein disclosedgas embodying the several featuresof the present invention, comprises a transversely movable worksupporting table and a rotary cutter spindle separately driven by meansof electric motors which are controlled through electrical connectionsadapted to permit a high degree of flexibility of control both forautomatic and manual operation of the machine.

In order to secure the high degree of accuracy and uniformity ofperformance required of machines of this type, it is necessary to drivethe table at all times at a uniform rate, and to bring the table to anabrupt stop at an exactly determined position, as for instance,v where amilling operation is being performed against a shoulder. With theconstruction herein dishclosed, these results are attained through thecontrol of the table motor which is driven at a relatively high rate ofspeed, and operates through reduction gearing to move the table at therelatively slow rate required for the most efficient operation of thecutter. In `order to stop the motor as rapidly as possible at the end ofthe table travel in either direction, electrical connections have beenprovided which will operate either in stopping or reversing thedirection of the table drive to electrically reverse the motor and thusapply a powerful braking action on the motor until it has been broughtsubstantially to rest. To bring the machine to a stand-still or toreverse and simultaneously to shift the intermediate gearing to a quicktraverse position, an extremely accurate and sensitive control of themain motor switch is required to brake the machine to a stop withoutcausing the motor tomechanically reverse or to kick with possible injuryeither to the work being performed, or to the machine itself. To

meet this requirement, in carrying out the prescnt invention, a noveland improved plugging or braking switch control mechanism has beendeveloped which is extremely sensitive to the direction and rate ofrotation of the motor to insure the bringing of the motor to a deadstop, and also operates to provide an accurate control for the shift toa quick traverse in an opposite direction if so desired.

A feature of the present invention comprises a novel and improvedviscosity switch which is adapted to be directly connected to thearmature shaft of the table motor, and to give uniform and eicientperformance at the high speed of operation attained by the motor, sothat an extremely accurate and sensitive switch control is obtainedwhich is controlled directly by the rate and direction of rotation ofthe motor. In order Ato prevent overtravel of the switch mechanism and aconsequent kicking of the motor in an opposite direction as the table isbrought to rest, a plunger or detent is provided which is electricallycontrolled by means of a solenoid. and is arranged in stopping themachine to drop into position to. prevent the movement .of theviscosityV switch in an opposite direction past neutraL position. Theelectrical connections for controlling the solenoid and plunger are soarranged as to hold the plunger in an inoperative position during themovement or reversal of the table, and permits the plunger to move intothe path of the switch only when the stop button has been pressed tobring the machine to a dead stop.

The viscosity switch employed in carrying out the present invention issupported directly on the motor shaft, and is constructed and arrangedto provide a relatively large peripheral surface which is immersed inoil, and is .quite unaffected by the speed of rotation of the rotatingmember. In order to brake the spindle and the motor connected thereto toa quick stop, a viscosity switch somewhat similar in form to thatemployed for the table motor has been mounted on the arm-ature shaft ofthe spindle motor, and is connected so that in stopping the spindle, thespindle motor may be electrically reversed until the motor and spindledriven thereby are brought substantially to a standstill. To furtherassist in stopping the spindle motor, there is also provided amechanical brake which is mounted at one end of the spindle motor, andoperates directly onthe motor shaft. With the present construction,electrical connections are provided which are arranged to permit theapplication of the mechanical brake only after the motor has beenbrought to a substantial stop by the operation of the plugging switchabove described. With this constructionl and mode of operation,excessive wear on the mechanical brake is avoided, while at the sametime the spindle is brought quickly and surely to a stop, and is firmlyheld against subsequent movement in either d1- rection by the operationof the mechanical brake.

This arrangement hasthe further advantage that the mechanical locking ofthe spindle against movement prevents any.rocking of the parts whichmight cause the motor to kick.

In accordance with another feature of the invention, the pick-olf gearsutilized for adjusting the rate of feed of the table, are housed withina casing which is constructed and arranged to permit access by theoperator thereto,

only when the table motor is entirely disconto, are spring-pressedplungers which are arranged when the casing cover is closed, to performthe double function of holding the operating pick-off gears in positionon the ends of the operating shafts, and to clamp the stored gearstightly in place to prevent possible rattling from the vibration of themachine.

Referring more specifically to the drawings, the work supporting tableof the machine as indica-ted at 8U is mounted for lateral movement onways formed on the base 82 of the machine. The milling cutter spindle asdesignated at 84 is rotatably mounted in a support 86 which isvertically adjustable with relation to the machine column 8B. As-shownin Fig. 1, a milling cutter 90 of ordinary description, is mounted indriven by means of an electric motor 94 whichforms an integral part ofthe spindle cutting unit mounted yin ,the support 86.

As best illustrated in Figs. 1, 2 and 3 of the drawings, the machinebase 82 is placed within a coolant trough.93 which extends across thefront of the machine, and along the sides and rear into eng-agement withthe lower end of the machine column 88. The coolant trough is vprovidedlalong its inner bottom edge' with two ilanges 95 Which provide 'asupport for the machine base, and also serve to assist in supporting thecoolant trough in close engagement with the machine base, so that anycoolant which may be used with certain types of milling operation, willbe caught and directed into the trough'as it ows down the sidesv of lthemachine base 82 from the point Where it is applied to the work at thepoint of cutting contact -ofthe milling cutter. As will readily be seenfrom Fig. 1 of the drawings, the

.inner walls of the coolant ytrough fit snugly against the base of themachine, so that the coolant will be drained off entirely away from thebase of the machine tov avoid so far as possible any corrosion of themachine which might arise from continued contact vwith the coolant. The

outer wall of the trough or vessel 93 has been extended at 91 to providefor the mounting of a coolant pump of ordinary description inthe trough?In order to provide a level support for the machinecolumn there is alsoprovided a llerplate 99 which is attached to the bottom edge of thecoolant trough and extends underI the column. Four bosses 'are formed onth'e corners of the ller plate to receive the weight of th'e machine.

The machine herein disclosed is controlled;

through electrical connections which are arranged to control theoperation of the two-speed reversible driving motor for the table, andalso the spindle motor, to secure a simple and elcient control of theseelements, for the power operation of the machine, by the operator orautomatically by means of dogs mountedA on the work supporting table.The rate and direction of the vmovement of the table is controlled bymeans of a simple arrangement of switchcontrol buttons which compriseleft and right feed buttons and left and right quick traverse buttons.These buttonsare mounted as indicated in Figs. `1 and 7, in acontrolpost 96 which is located adjacent one side of the table. Thesebuttons are arrangedin two series, and comprise four buttons 98 mountedin vertical alignment on the table side ,of the controlpost. v tocooperate with corresponding dogs on the table to control the directionand rate of feed of the table, and a second series ofl manuallycontrolled buttons mounted'on the opposite side of the control, post topermit the convenientoperation of thecontrols by hand. Two additionalstop buttons |02 are provided for engagement with corthe movement of thetable in either direction. The general features of the electricalcontrol system outlined above are similar to those illustrated anddescribed `in the copending application of Graves and Bennett, SerialNo. 714,809, led

March 9, 1934, and will not therefore be further described, except in sofar as necessary in connection with the subsequent description oftheelectrical diagrams Figs. 23 and 24 of the draw'- ings illustratingthe several-features of the'lprs-" slow feed and quick traverse geartrains. These connections include a pinion |36 mounted on the armatureshaft |38 of the motor, and adapted to mesh with alarge pinion |40 onaparallel operating shaft |42. On the forward end of the shaft |42 ismounted a pick-off gear |44 which meshes with acorresponding pick-01Tgear I 46v A second pick-off` on a short operating shaft |48. gear |50on the shaft |48 engages with a gear |52 on an operating shaft |54 whichcarries a driving worm |56. Meshing'with the worm |56 is a worm gear |58which is loosely mounted to turn on a shaft |60, and has also formedthereon an internal clutch gear |62 adapted to engage with a slidingclutch member |64. The clutch member |64 is continuously in mesh withlan idler gear f |66 which meshes in -turn with a split feed nut |68screw-threaded on a feed screw |10 which is in turn supported againstaxial movement with relation to the table 80. The table may be drivenalternatively at la quick traverse rate through gear connections whichinclude a spiral gear |14 on the shaft |42, and a spiral gear |16 whichis loosely sleeved to turn on the shaft |60 andhas formed on one facethereof a clutch member |18 .adapted to engage with a correspondingclutch face on the clutch member |64. fThe position of the clutch member|64 is controlled by means of a control rod |80 which is journalledwithin the shaft |60, and is keyed for axial movement with the clutchmember. A spring |82 coiled within a sleeve |84 fitted over one end ofthe control rod |80 and'adapted to bear against a block |86 secured tothe control rod,.tends normally to push the rod and the clutch to theleft as shown in Fig.

10, to maintain the clutch normally .in its slow feed position. In orderto shift the clutch to its quick traverse position, a solenoid indicatedat |88 in Fig, l0, is provided with a plunger |90 connected by means bofa link |92 with a bellcrank clutch control lever |94 which is mounted toturn about a pivot |96, and is provided with a yoke and a' collarsecured thereto, which rides in a corresponding annular groove |88 onthe control rod |80.

v An oil pump for supplying lubricant to the various vparts ofthemachineis illustrated in Figs. 11 and 12. This pump comprises a hollow pistonrod |91 which is actuated by an eccentric pin |99 secured inthe end ofthe shaft |42 and engaging between two collars secured to the pistonrod.

The pick-off gears are contained within a ca sing 200 which is providedwith a cover 20| arranged to swing about a pivot 202 isee Figs. 1 and11). Two spring-pressed plungers 203 seat- .ed in recesses formed in thecasing 200 adjacent the pivot 202 are arranged for engagement withbearing surfaces 204 Aon a bearing member or l plate 205 adjustablysecured to turn with the cover 20| about the pivot 202, so that thecover when released will tend automatically to swing to an openposition. An additional spring plunger 806 see Figs. 1, 4 and 6),similarly seated in a revcess in the casing is arranged for yieldingengagement with the opposite side of the cover 20| at a point adjacentthe locking device hereinafter to be described. The spring plungers 203and '206 perform an additional function of taking up any possible playwhich may be present in the pivot gr lock 'for-the cover 20| and thusprevent any possible looseness or rattling of the parts.

The casing is provided with three supporting pins 201 for storingadditional pick-olf gears, these pins being located in alinementrespectively .with the three'operating shafts |42, |48 andl |54.

Each pin is j ournalled to receive a plunger 208 which is provided atits outer end with anA enlarged head to engage with the correspondingpick-oir gear supported in operative position on the end of thecorrespondingoperating shaft. A coil spring 2I0 is mounted oneachplunger 208A bearing at one end against the head of the plunger andat its other end against the pick-off gears stored on a pin 201, so thatthe springs perform the double function of holding the operative-pick-of gears in position on the ends of their respective shafts, andalso maintain the stored gears iirmly in position against the base ofthe pins 201 to prevent possible shifting or rattling of the gears whenthe casing cover is in its closed position.

With the present construction, the casing cover Y 20| is normally heldin closed position by means of` a locking device which is interconnectedwith a stop switch in the main connections to the table motor, so thatit can be released to permit the opening ofthe cover 20| only after theswitch has been moved to open or stop position. Ihe locking devicecomprises a locking lever 220 (see Figs. l, 4, 5 and 6) which is securedat its upper end to a rock shaft 222 and extends downwardly through anaperture 224 formed in the machine casing. At its lower end the lockinglever 220 is provided with a wedge-shaped projection 226 which isarranged to extend within a recess 228 formed in the upper left handcorner of the cover 20| as viewed from the front of the machine, and tomove into locking engagement with a correspondingly shaped groove 230 atone end of the recess 228 to lock the cover in closed position. Theposition of the locking lever 220 may be controlled manually to lock orrelease the cover by means of a hand lever 2,36 which is also rigidlysecured to the rock shaft 222, and carries at its free end an axiallymovable detent pin 238 adapted to engage with either of two holes 240corresponding to the open and closed positions of the locking lever 220.A knurled handle 242 is tted tothe forward end of the detent pin 238 topermit the detent pin 238 toA be conveniently withdrawn or fitted intoeither of the holes 240.

' In accordance with one feature of the invention a mechanical interlockis provided between the mechanism for locking the pick-olf gear cover inplace and the stopvswitch connections for the table motor which is soarranged as to prevent the operation of the locking lever to open thecover until after the manually operable stop button provided with thepresent machine has been pressed to disconnect the table drive,` and isfurther arranged so that the movement of the locking lever to openposition will operate automatically to open a special safety stop switchto wholly disconnect the table motor from its source of electricalsupply as hereinafter more fully described.

The mechanical interlock .between the manually operable stop switchreferred to, and the locking lever 220 for the pick-off gear cover 20|is arranged to prevent the opening of the cover 20| except when theswitch is open, and prevent the closing of the switch until aiter thelocking lever has been returned to locking position. To this end thereis also secured to the rocl; shaIt 222 to move with the locking lever226, a laterconnected to the manually operable stop switch hereinaftermore fully described The manually operable stop switch for the tablemotor, as best shown in Figs. 1 and 4 to 9 inclusive, compnses a stopbutton 250 which is mounted on the outer end of a plunger 252 which atits inner end engages with two switch levers 254 which are mounted toturn respectivelyon the vertical pivot posts 256, and engage at theirfree ends with the usual stop switch contact plungers 258. Directlybelow the stop buttonl 250 there is provided a reset button 260 which ismounted on the outer end of a spring-pressed reset plunger 262. Theplunger 262 is connected by a small bell-crank 264 pivoted at 256 to thelower end of.

a vertical plunger 268 which is arranged to bear at its upper endagainst the stop button plunger 252. When the manual stop button 250 ispressed. causing the plunger 252 to be moved inwardly, an annular groove210 in the plunger 252 is brought into alignment with the verticalplunger 288, so that the plunger 268 is permitted to move upwardly, andthe reset plunger 262 and reset button 260 to move outwardly under thepressure of their spring 212, thus locking the switch conl nections instop position until the reset button However when the reset button ispermitted to move outwardly upon the pushing of the stop button 25D, asabove described, a V-shaped groove 216 in the plunger 262 is broughtinto alignment with the V-shaped portion 214 of the lever arm 244, sothat the locking lever 222 may be moved about its pivot into openposition. With this arrangement of the parts, it will readily be seenthat it is impossible again to move the reset button inwardly until thelocking lever 220 has been again returned to its locking position, thusreducing tl a minimum the possibility .that the machine may beaccidentally started before the operator has completed the operation ofsetting up the machine. t

With the construction and arrangement of the electrical controls for thework supporting table herein described and illustrated, and particularlywith the plugging switch connection disclosed, it has been found evenwith the machine in stopped position with the manual stop button engagedas above described, that the accidental rotation of the spindle motorcan act to close one of the plugging switch contacts, and

thus cause the motor to kick. In order to avoid' any possibility ofhaving the motor kick while the operator is changing or adjusting thepickoi gears above described, there is also provided with the presentconstruction, a. safety stop switch which is controlled automatically bythe movement of the pick-oil` gear cover locking lever 220 to openposition, to disconnect the main controis for the table motor, so thatthe motor cannot start or run when the switch is open. This ,switch isentirely independent of the switch contacts above described which arecontrolled by the stop button 250.

With the present construction, the movement of the locking lever 220 toopen position to permit the opening of the pick-oli gear casing cover20|, is also arranged to open the switch contacts for the table motor.as best shown in Figs. 4, 5 and 6 of the drawings, the safety stopswitch comprises a switch contact plunger 288 with movable contact arm282 which is arranged for Aengagement with the corresponding stationarycontactors 284. A spring 288 coiled about the rear end of the plunger288 tends normally to maintain the switch in closed position with thecontact arm 282 in engagement with the stationary contact member 284.The position-of the switch plunger 288 is controlled by means of a leverl0 298 which is adapted to turn yabout a pivot 282 and has formed on thehub thereof an arm 23a which is adapted for engagement with a camsurface 388 formed on the end of'the laterally extending locking levervarm 244. The movement of the locking lever 220 to its open position,causes the cam-shaped portion 388 of the lever arm 244 to engage withand swing the lever arm 294 about l'ts pivot to disengage the safetystop switch members 282 and 284, thus disconnecting the switch" posts|96, and is adapted for engagement with an arm 296 which forms a part ofthe lever 2,98 30 controlling the position of the plunger 288. Thepressing of the spindle jog button 382 by the operator, causes the rearend thereof to engage with the arm 296 to rotate the switch lever 298 tothe fullest extent about its pivot against the '35 pressure ofthe spring288 to engage a movablel contact member 283 with the stationary contacts286, thus closing the circuit through the switch leads 2--35 as shown inthe electrical diagrams Figs. 23 and 24, to start the spindle 40 motor.

As has been stated, in accordance with another vfeature of the presentinvention, a novel 'and improved plugging switch is employed forelectrically reversing the table motor which is ar- 45 ranged uponoperation of the stopping switch to operate uniformly and efllciently toelectrically reverse and brake the motor and table driven thereby to astop, and thereafter to cut olf the motor without causing the motor tomechani- 50 cally reverse or kick in an opposite direction.

The plugging switch employed, as best shown in Figs. 11, 14 and 15,comprises a viscosity switch of new and improved construction which ismounted directly on the armature shaft |38 of 55 the motor, and isparticularly well adapted for' smooth and efficient operation at therelatively high speed of rotation attained by the shaft. 'Ihe viscosityswitch employed comprises two drum-shaped members 3|8 and 3|2 rigidlyseocured by means of a clamping vnut 3I4 to the reduced end of the shaft|38 to rotate therewith, and a hollow drum-or band 3|6 which is fittedover the drums 3|8 and 3|2, and is provided in ternally with a centralrib 3|8 which projects 65 between and is supported by roller bearings328 on the reduced end portion of the armature shaft |88.` The lowerportion of the inner drums 3|8 and 3|2l and outer drum 3|6 are immersedin an oil bath provided within a casing 322 which sur.,

To rounds the enduof the armature shaft |38. As best shown in Fig. 14,the central bottom portion of the outer drum or band 3|,.6 vis cut awayto f provide access of the oil to the yrotating drums 3|8 and 3|2. Theouter drum or band 3|6 is 'in an advanced position with the contacts 332in engagement'with the stationary contacts 336. The contact plunger 338is similarly provided with movable contacts 348 which engagealternatively with the stationary contacts 342 and 344, being normallyheld in engagement with the contacts 344 bymeans of a compression spring346.

With the construction and mode of operation of the switch disclosed, itwill'readily be seen that a relatively slow ro'tation of the shaft |38and the drums 3|8 and 3|2 will operate to set up an oil film between theperipheral surfaces of these drums and the' inner peripheral surface ofthe drum 3|6, which will-operate to rotatepthe drum and lug 328 mountedthereon to operate one or` the `other of the switch plungers 328 or 338'againsty the pressure 'of the relatively light springs 338 or 346 'tooperate the switches. creased speed of rotation of the shaft |38 as themotor is brought up to speed cannot in any way affect the integrity orefficiency of the oil film, inasmuch as it is positively maintainedwithin the inner peripheral surface of the drum 3|6, so that the drum ismaintained at all times in the required angular position until the motorand armature shaftr |38 are again brought-substantially to a standstill,when the pressure of the switch plunger spring becomes effective to.return the switch drum 3I6 to its neutral position.

In accordance with one feature of the present invention, a switch lockhas beenprovided for the table viscosity switch above described,controlled by means of a solenoid, and adapted to prevent overtravel ofthe switch mechanism when the table motor is plugged to a stop.l Withoutthe switch lock -the plugging switch operating at a The inrelativelyslow rate of speed would depend on the centering springs 338 and346'formthis purpose. It has been found, however, that while thestrength of the centering springs may be adjusted to cause the contactsof the viscosity switch to open at predetermined speed to determine thepointvof stopping of the motor, variations in temperature andconsequently of the viscosity o'f the `oil will vary lthe action of thesprings sufficiently to produce errors in the point of stopping, and mayeven tend to set up an oscillatory condition whereby the rocking motionof the viscosity switch would control the motor reverse contactors insuch a manner as to continue its ownl rocking action indefinitely; Withthe present construction, the tension of the centering springs is madesufficiently light so that the contacts will always open at or near zerospeed of the table motor. There is also provided a-latch 358 which isadapted when rendered operative to move into the path of a plate 352mounted on the bracket 324, and thus to prevent the movement of theswitch drum 3|6 beyond its neutral position, as illustrated in Fig.

l5. The latch 358 is mounted in the lower end of an armature shaft 354of a solenoid 356 supported directly above the viscosity switch. Thesolenoid operates normally while energized to maintain the latch 358 inretracted inoperative position',-

. ture shaft and latch 350 to drop into the path of the plate 362. Theoperation of the solenoid 356 is controlled by means of electricalconnections hereinafter described, being energized at all times duringthe operation or reversing of the `table, and being de-energized only bythe pressing of one of the stop buttons and consequent dropping out ofthe contacts 2-|1 of the secondary relay coil LR or RR (see Figs. 23 and24) to stop the operation of the table.

The cutter spindle 84 is driven from the spindl motor 94 through drivingconnections which include a bevel gear 360 rigidly secured to thespindle 84, and a bevel pinion 362 meshing therewith which is secured toone end of a short shaft 364 set at right angles to the spindle 84. Apickoil. gar 366 supported on the other end of the shaft 364 engageswith a pick-off gear 368 supported on a stub shaft-310 which alsocarries a gear 312 arranged to mesh with a pinion 314 mounted on thearmature shaft 316 of the spindle motor 32.

'I'here is also supported on the amature shaft 316 of the motor 94, amechanical braking device which comprises a circular frame or hub 318keyed to turn with the armature shaft 316 and having formed thereonexternal gear teeth to mesh with corresponding internal gear teeth of aflat braking ring 380 which is fitted between a stationary ange 382which forms a part of the motor casing, and a movable braking disk 384which is keyed against rotational movement by the engagement of externalgear teeth formed vin the disk with corresponding internal gear teethformed on the internal periphery of the casing. In order to apply abraking force to arrest the rotation of the motor shaft 316, the movablebraking disk 384 is moved axially to frictionally engage the rotatingbrake disk or flange 382 between the stationary :flange 382 and the disk384. To this end the movable disk 384 is screw-threaded to a post 386which is rotatably mounted in bearings formed in the end plate 388 ofthe support 86. The angular position of the post 386 is determined tocontrol the application of the brake by means of a lever arm 390 securedthereto, which is connected at its free endby means of a short link 392,to the armature shaft 394 of a solenoid 396. A tension spring 398connected at one end to the lever arm 390 and at its other end to a pin400, tends to move the lever arm 390 iny a clockwise direction, as shownin Fig. 19, to set the brake. During the operation of the spindle motor,the

solenoid 396 is energized to move thearm 390 ip a counterclockwisedirection against the pressure of the spring 398 to release the brake.

In accordance with one feature of the present invention, electricalconnections have been provided for electrically reversing or pluggingthe spindle motor 94 substantially to a stop, and

thereafter for de-energizing the brake solenoid 396, so that the spindleis rst considerably retarded by the electrical braking action of themotor itself, and themechanical brake is then utilized to completelystop and to maintain the spindle in stationary position with a minimumof wear upon the brake itself. To this end a viscosity plugging switch,as best shown in Figs. 16, 21 and 22, has been mounted on the armature.shaft 316 of the motor. This switch, which is similar in many respectsto that above described drums 402 and 464 secured to turn with themoto;-

shaft 316, and a switch drum 406 which is mounted thereon and has formedon its inner periphery a rib 406 which extends between the drums 402 and404 into engagement with a roller bearing 4|0 on the motor shaft 316.The lower portions 8 of the drums 402 and 404 and switch drum 406 areimmersed in an oil bath provided in the motor casing. The switch drum406 is provided on its upper side with a lug 4|2 to which is secured oneend of a switch plunger 4|4 which carries the movable contacts 4|6arranged for engagement alternatively with the stationary contacts 420and 422. The switch drum 406 and switch plunger 4| 4 are normallymaintained in a neutral inoperative position by a spring balancingdevice comprising a rod 424 which is connected at one end to the lug 4|2and extends through a stationary sleeve 426 and two coil springs 428 and430 which are coiled about the rod 424 at each side of thestationarysleeve 426, and tend normally to malntain the switch drum 408and switch plunger 4 I4 in the intermediate position illustrated inFigs. 21 and 24. The centering springs 428 and 430 are preferablyadjusted with a light tension to cause the contacts to be opened at ornear the zero speed of the spindle motor, the action of the mechanicalbrake above described being sufficient to prevent the undesirableoscillating or rocking of the motor above described in connection withthe table viscosity switch.

Another feature of the machine illustrated in the drawings, consists ina. take-up device to maintain a tight working engagement between the'feed nuts and the feed screw of the table` drive, together with meansfor easing ofi this 35 mechanism during the quick traverse operation ofthe table. This mechanism is similar in many respects to thatillustrated in the copending application of Graves and Bennett, SerialNo. 714,808, med March 9, 1934,/for Machine tools, but may 4 be briefiydescribed in connection with Figs. l0,

.11 and 13 of the drawings. As previously pointed out, the table isdriven through connections which comprise the feed screw |18 secured tothe table and the feed nuts |68 which are driven 4 in unison from thedriving gear |66. In order to take up any lost motion which may existbetween 'the feed screw |10 and nuts |68, a cam member 425 is sleeved onthe hub of one of the feed nuts |68 between a roller bearing formedintegrally with the hub of'the nut |68 and a cooperating cam face 421formed on one ofthe stationary bearings for the nut. The position of thecam member 425 is controlled by means of a rock shaft 429 which hasformed on one end thereof 5 a pinion arranged to mesh with a gearsegment formed on the lower side of the cam member 425. On the other endof the shaft 429 there is provided an arm 43| which, is operativelyconnected to a control rod 433 secured to move Verticaily with thearmature of the quick traverse clutch solenoid |88. The arm 43| isforked to extend at either side of the rod 433, and is engaged fromabove by the vfixed collar 435 and from below by a spring-pressed collar431. With this construction the downward movement of the armature |90and control rod 433 to shift the quick traverse clutch to quick traverseposition positively rocks the shaft 429 and arm 43| to ease off thetake-up 'device. 'I'he upward movement of the control rod 433 with thearmature |90 to return the clutch to the slow feed Y vpositionillustrated in Fig. 13, causes the arm 43| and shaft 429 to be rocked inan opposite direction to take up any lost motion between the feed Thestarting of the table motor causes the switch trical connections forcontrolling the operation of the table and the cutter spindlerespectively through their driving motors will be briefly described inconnection with the electrical wiring diagram Fig. 23 and theexplanatory diagram (Fig. 24 so far as necessary to make clear theconnection therewith of the several new and improved features ofconstruction and operation of the machine above set forth.

The table driving motor and spindle drivingl motor are driven from athree-phase power line designated as L1, L2 and L3. The table motor iscontrolled by means of a reversing switch having two exciting relays Land R.

The mainswitch for the table motor is supported on a panel indicated indotted lines. at 432 in Fig. 23, andcomprises two sets of contacts whichare controlled bythe relay coils R and L respectively to connectthemotor and table lfor right or left hand operation. A high spee'd and lowspeed .switch for the table motor is mounted on a second panel indicatedat 434 in dotted lines, and comprises two sets of contacts controlledrespectively by the relay coils HS and LS for high speed or low speedoperation ofthe table motor.

On another panel indicated at 436 in dotted lines, are carried the mainswitch contacts for the spindle motor 94 controlled by means of tworelay coils SF and SR for opposite directions of rotation of the motorand spindle driven thereby.

There are also provided on a panel 438 designated in dotted lines inFig. 23, three secondary relay switches which are arranged to controlthe operation of the table and spindle switches above' described,together with the solenoid 288 which operates the slow feed and quicktraverse clutch 264. These secondary relays comprise the secondary coilsLR and RR controlled respectively by the left and right feed buttons',the coils TL and TR controlled respectively by the left and right quicktraverse buttons, and a secondaryl relay coil RC which controls theoperation ofv the slow feed and quick traverse solenoid |88, and alsohas connections which are arranged under certain operating conditions tocontrol the operation of the high speed table motor and the spindlemotor switches.

Starting with the machine at rest, pressing the feed left button willenergize the LR coil, so lthat the LR contacts 2-24 open, LR contacts4--1 close, forming a holding circuit, the LR contacts 2-|8 closeenergizing the main contactor coil L starting the motor, LR contacts2|1'close to energize the latch solenoid 356 in the table viscosityswitch, and LR contacts 2-3I close` to energize SF coil and thus startthe spindle motor.

drum 3|6 of the table motor viscosity switch to swing to the right asshown in Fig. 15, carrying with 'it the switch contact members 340,opening the, switch 6-23 and closing the switch 24-25. Similarly, thestarting of the spindle motor upon the energizing of the SF coil willcause the switch drum 4-6 of the spindle motor viscosity switch tomove-to the left as illustrated in Fig. 2l, carrying with it the switchcontacts 4|6 to close the switch plugging contacts 2-32. The energizingof the SF coil simultaneously causes the SF contacts 32-33 to fopen. Thepressing of the feedV right button will operate similarly to start the 5machine with. the table moving tothe right.

lclutch -.to quicktraverse position. `3|-'-35 open preventing thespindle from starting,

Assuming the table is feeding left with the coils l LR, L and SFenergized-and the table viscosity switch contacts 22-6 and 24--25closed, and that it is desired to stop the machine by pressing the lstopleft button, the operation of the electrical connections is asfollowsz-The pressing of the stop left button de-energizes the coil LRso that LR contact 2-I8 opens dropping out of the main contactor L, LRcontact 2-24 closes and establishes a circuit'to the main contactor coilR through viscosity switch contacts 24-25, thus electrically reversingor plugging the table motor, LR contacts 2-3I open, but the spindlecontactor is held in through the SF interlock 2li-3| and L or Rinterlock 2--2 9, and LR contacts 2| 1 open, de-energizing the solenoid35B in the viscosity switch so that the latch 350 ispermitted t'o dropinto the path of the bar 352. When I'the motor has practically stopped,the switch contacts 24-25 are opened by the movement of the switch drum3|3 back to its central neutral position under the influence of thespring 346, being,

bar 352 on the switch drum 3|6. The opening of the contacts 24-25de-energizes the main contactor L, thus disconnecting the table motor.In-

terlock 2-29 controlled by the L coil disconnects the spindle contactorSF. Inasmuch as the contacts 2-32 of the spindle viscosity switch arethe SRjcoil which in turn disconnects the spindle motor and the brakesolenoid 396 to permit the application ofthe mechanical brake.

Assumingthat it is desired to operate the table at-a quick traverse rateto the left from a rest position,'the pressing of the fast left buttonwillenergize vthe TL coil." The TL contacts |0-1 close and energize theLR coil. TL contactsy 2li- 2| and 2|-22 close and energize the coilRC-through plugging switch contacts 22-6. The closing of the circuitthrough the RC coil acts through the When the motor contacts L 2 1!) toenergize the'slcw feed and quick traverse clutch solenoid 288 to shiftthe RC contacts vunless the spindle'selector switch having contacts3|-35 is in continuous position. RC contacts 26-6 also open tode-energize the contactorl coil LS, and RC contacts 2-21 close toenergize the high speed coil HS,` if this coil has not been previouslyenergized vby th-e operation of the mer- `cury switch indicated in Figs.23 and24. The closing of the relay coil LR starts the table motor in themanner previously outlined inconnection with star-ting from rest to feedleft.

If it is now desired to stop the machine opera ing to the left at aquick traverse rate, the pressing of the stop' left button'will operateas followsz-At this time the coils LR, lTL, L, RC-and the quick traverseclutch solenoid 288: are energized. Pressing the stop buttonde-energizes LR and TL. The energizing of, the LR relay in conjunctionwith the viscosity switch plugs the table motor to rest in a mannerpreviously outlined instopping from feed. The opening of TL contacts2|J2| de-energizes the relay RC. The RC contacts 3l-35`close, but thespindle is prevented the LR relay has been fle-energized and the spindlemotor interlocks 29-3l which open.

Assuming now that the table is operating at a. slow feed to the left andthat it is desired to shift to a quick traverse rate to the right, thecontactors LR, L and SF are closed as well as the table motor viscosityswitch motor contacts 24--25 and 22--6. The pressing of the fast rightbutton will energize the coil TR. TR contacts |-l2 close, energizingcoil RR, and TR contacts 2l-23 and 20-2! close, but viscosity switchcontacts 6-23 are opened, so that the relay coil RC is not energized atthis time, RR contacts 2-4 open, deenergizing the LR relay which in turnde-energizes .the main contactor coil L, RR contacts |3-I2 close forminga holding circuit throughA the LR contacts 2-l3 which also close, and RRcontacts2-25 close to energize the main contactor R, electricallyreversing the table motor. When the motor has practically stopped, theviscosity switch contacts 23-6 are closed by the movement of the switchmotor 340 and switch drum 3| 6 to their neutral position under thepressure ofthe spring 346 as illustrated in Fig. to energize the relaycoil RC. The energizing of the RC relay operates as above described toenergize the slow feed and quick traverse solenoid 288, disconnects thespindle motor, and shifts the table motor from 'slow speed to high speedas above` described.

If it is now desired to shift from a rapid traverse to the left to arapid traverse to the right, the. relay coils LR, TL, L, RC and HS andthe clutch .solenoid |88 being energized as above described,

the pressing of the fast right button energizes TR causing TR contacts2li-2l to close, holding th-e RC relay in through its interlock 2l-6,and TR contacts l2-l5 close energizing the relay coil RR. The RRcontacts 2-4 open de-energizing the relay coil LR, RR contacts I3-I2close, forming a holding circuit, and RR contacts 2-25 close to energizethe R coil after the LR A'contacts 2-I8 have released the main contactercoil L.

The invention having been described, what is claimed is:

1. In a milling machine, the combination of a power driven member,driving connections therefor including a reversible electric motor anda. shaft directly driven thereby, a switch controlling mechanism forcontrolling the operation of said motor and member driven therebyincluding starting, stopping and reversing switch conmechanism forcontrolling the operation of saidA motor and member driven thereby`including starting, stopping and reversing switch contacts, a.viscosity plugging switch mounted on said shaft having a central stopposition and alternative operating positions controlled bythe directionof rotation of the motor, centering springs of a strength to cause theviscosity switch to return t0 central stop position at or near zerospeed of rotation of the motor, and mechanical means rendered operativein plugging the motor to 4rest to positively arrest the return movementof the viscosity switch under the influence of the springs in stopposition.

3. In a milling machine, thecombination of an operating tool, a worksupporting table movable'to position work with relation to said tool,driving connections for the table including a reversible motor, a switchcontrol mechanism for controlling the operation of said motor and tableincluding starting, stopping and reversing switch contacts, a viscosityplugging switch for the motor having a central stop position andalternative operating positions controlled by the direction of rotationof the motor, means tending to maintain said viscosity switch yieldinglyin stop position, and mechanical means rendered operative in pluggingthe motor to rest to positively arrest the return movement of theviscosity switch in stop position.

4. In a milling machine, the combination of an operating tool, a worksupporting table movable to position work with relation to said tool,driving connections `for the table including an electric motor, and aswitch control mechanism for controlling the operation of said motor andtable including starting, stopping and reversing switch contacts, aviscosity plugging switch for the mctor having a central stop positionand alternative operating positions controlled by the direction ofrotation of the motor, means tending to maintain the viscosity switchyieldingly in stop position, a solenoid, a plunger controlled therebyadapted when renderedr operative to lock the vviscosity, switch againsta return to the alternative operating position, and means forcontrolling the operation of said solenoid in stopping the machine toprevent overtravel of the switch mechanism in plugging the motor to astop.

5. In a milling machine, the combination of an operating tool, a worksupporting table movable to position work with relation to said tool,driving connections for the table including an electric motor, switchcontrol mechanism for controlling the operation of Said` motor and tableincluding starting, stopping and reversing-switch contacts, a viscosityplugging switch for the motor having va. central stop position andalternative operating positions controlled by the direction of rotationof the motor, means tending to maintain the viscosity switch yieldinglyin stop position, a solenoid, a plunger controlled thereby arranged whenrendered operative to engage with and'prevent the return of thelviscosity switch from one to the other of said alternative operatingpositions, and

electrical connections to said solenoid rendered trolling the operationof said motor and table 'including starting, stopping andreversing-switch contacts, a viscosity plugging switch for the m0- torhaving a central stop position and alternative operating positionscontrolled by the direction of rotation of the motor, means tending tomainto engage with and prevent the movement o! the plugging switch pastsaid stop position from one tothe other of its alternative operatingpositions, and means rendered operative by the actuation of saidstopping switch contacts to render said mechanism operative to preventthe return of said switch past stop position.

7. In a machine tool, the combination of a' power driven member, drivingconnections therefor including an electric motor and a shaft directlydriven thereby, and electrical switch connections for controlling theoperation of the motor including a viscosity plugging switch comprisinga drum secured to rotate with said shaft, a switch control bandsurrounding and mounted to turn freely with relation to said drummeanstending yieldingly to maintain said band in a predetermined stationaryangular position, means forF supplying oil to the periphery of said drumto move the band in the direction of rotation of the drum, and aswitch'member connected to. said band arranged to be closed by themovement of l said bandfrom said stationary position.

8. In a machine tool, the combination of a power driven member, drivingconnections-therefor including an electric motor and a shaft directlydriven thereby,'and electrical switch connections for controlling theoperation of the motor including a viscosity plugging switch comprisinga drum secured torotate with said shaft, a switch control bandsurrounding and mounted to turn freely with relation to said drum, meanstending yieldingly tomaintain said band in a predetermined stationaryangular position, means for supplying oil to the periphery of said drumto move the band in the direction of rotation of the drum, and a switchmember connected to said band having neutral and alternative operatingpositions controlled by the direction of movement of said band under theinfluence of the oil between the band and,rotating drum.

9. In a machine tool, the combination of a power driven member, drivingconnections therefor including an electric motor and a shaft switchmember connected to said band and having a central neutral positioncorresponding to v said stationary position of said bandA andalternative operating positions determined by the movement of tliebandin opposite directions under the influence of the oil fiow between theband and rotating drum.

10. In a machiner tool, the combination of a power driven member,driving connections therefor including an electric motor, a mechanicalbrake for'the motor, a switch controllingmechanism including'a motorstopping switch, electrical connections' controlled by said switch forelectrically braking the motor to rest, means controlled vby said switchfor applying said mechanicalbrake, and control means for actuating saidmeans to set the brake only as the motor reaches substantially a stopposition.

11`. In a milling machine, the-combination of a power driven member,driving connections the spring, electrical connections for controlling'the operationof the motor including a plugging therefor including avreversible electric motor, a lmechanical brake for the motor, a'switchcontrolling mechanism including a motorI starting and stopping switch, amotor plugging'switch for electrically reversing and plugging the motorAto a stop, electrically actuated meansfor controlling the operation'ofthe brake, and electrical connections'rendered operative in stopping themotor to cause said means to set the brake only as the motor reachessubstantially, a stop position. y

A12; In a milling machine, the combination with a work supporting table,of a rotary tool spindle, a motor connected to drive the spindle, amechani- 4cal brake for the motor, electrical connections forcontrolling the` brake, and an electrical control system comprising astarting and stopping switch for the motor, a motor plugging switchhaving operating and neutral rest positions for electrically reversingand pluggingthe motor to a stop, and means controlled electrically bysaid plugging switch and rendered operative by the return of saidplugging switch to neutral ,position tol setl the brake as the motorreaches substantially stop position. Y

13. In a milling machine, the combination with a work supporting table,a rotary tool spindle, a i

reversible spindle motor connected to drive the spindle, a mechanicalbrake for the motor, spring means tending to set the brake, abrakesolenoid arranged when energized to maintain the brake in off positionagainst the pressure of the spring, and electrical connectionscontrolling the operation of the motor including starting, stoppingandreversing switch contacts, a plugging switch having'a central stopposition and alternative operating positions controlled by the directionof rotation of the motor, means tending to maintain said plugging switchyieldingly in rest position, and connections arranged upon the return ofthe plugging switch to stop position to de-energize the :sol

solenoid and set the brakev at substantially zero speed of rotationofthe motor.

14. In a milling machine, the combination with a work supporting table,of a rotary tool spindle, a motor connected to drive `the spindle, amechanical brake arranged when rendered operative to brake the motor andspindle connected thereto, a switch'controlling mechanism including aspindle motor stop switch, electrical connections controlled by saidswitch for eleetrically braking the motor to rest, means controlled bythe move-- ment of said switch for applying said mechanical brake, andcontrol means for actuating -said kmeans to-set the brake only as themotorreaches substantially stop position. I

15. In a milling machine, the combination with a work supporting table,of a rotary tool spindle, a motor connected to drive the spindle, amechanical brake arranged when rendered operative to brake the motor andspindle connected thereto,

a 'brake solenoid arranged when energized to 1 maintain thebrake invoflposition, electrical connections for controlling the Amotor including aplugging switch for electrically reversing and plugging the motor to astop, and electrical connections to lcle-energize the brake solenoidsimultaneously with the release of the plugging switch as the motor isslowed to rest.

16. In a milling machine, the combination with a-work supporting table,of a rotarytool spindle, a

'spindle motor connected to' drive the spindle, "a mechanical brakeforthe motor and spindle, spring means 'tending to set the brake, abrake solenoid arranged when energized to maintain the brake in orfposition against the pressure of

